Upregulation of KCC2 Activity by Zinc-Mediated Neurotransmission via the mZnR/GPR39 Receptor

Abstract

Vesicular Zn2+ regulates postsynaptic neuronal excitability upon its corelease with glutamate. We previously demonstrated that synaptic Zn2+ acts via a distinct metabotropic zinc-sensing receptor (mZnR) in neurons to trigger Ca2+ responses in the hippocampus. Here, we show that physiological activation of mZnR signaling induces enhanced K+/Cl− cotransporter 2 (KCC2) activity and surface expression. As KCC2 is the major Cl− outward transporter in neurons, Zn2+ also triggers a pronounced hyperpolarizing shift in the GABAA reversal potential. Mossy fiber stimulation-dependent upregulation of KCC2 activity is eliminated in slices from Zn2+ transporter 3-deficient animals, which lack synaptic Zn2+. Importantly, activity-dependent ZnR signaling and subsequent enhancement of KCC2 activity are also absent in slices from mice lacking the G-protein-coupled receptor GPR39, identifying this protein as the functional neuronal mZnR. Our work elucidates a fundamentally important role for synaptically released Zn2+ acting as a neurotransmitter signal via activation of a mZnR to increase Cl− transport, thereby enhancing inhibitory tone in postsynaptic cells.

Regulation of neuronal chloride homeostasis by neuromodulators

“…2000) where it acts via postsynaptic metabotropic Zn 2+ receptors (mZnRs) on CA3 pyramidal neurons (Chorin et al . 2011). At this synapse both extracellular application and synaptic release of Zn 2+ , which activate mZnRs, increases KCC2 surface expression and transporter efficacy.…”

Engagement of the GABA to KCC2 Signaling Pathway Contributes to the Analgesic Effects of A3AR Agonists in Neuropathic Pain

“…Lifetime images were acquired every 10 s for a period of 7 min. After a control period of 50 s, perfusion solution was switched to ACSF containing 15 mM KCl (osmolarity adjusted using mannitol) to reverse KCC2-mediated Cl Ϫ transport (Chorin et al, 2011). Lifetime measurements were compiled over time after the switch in extracellular [K ϩ ] to quantify the rate of Cl Ϫ import in cells through KCC2.…”

Zinc ions upregulate the hormone gastrin via an E-box motif in the proximal gastrin promoter

“…To determine whether GPR39 has any role in the stimulation of gastrin transcription by Zn 2C ions, the effect of GPR39 knockdown on gastrin promoter activity was investigated. A previously validated siRNA sequence CCATGGAGTTCTACAGCATtt which was effective in knocking down GPR39 expression in the neuronal SHSY-5Y cell line (Chorin et al 2011) and in HT29 colonocytes ) was used. AGS cells were co-transfected with a gastrin promoter luciferase construct (365pGASLuc) and either 100 nM GPR39 siRNA or 100 nM Lamin A/C siRNA as a control.…”